Question

EASY PERL QUESTIONS

1. Write a subroutine, called above_average, which takes a list of numbers and returns the ones which are above the average (mean). (Hint: make another subroutine that calculates the average by dividing the total by the number of items.) Try your subroutine in this test program.

my @fred = above_average(1..10);

print "\@fred is @fred\n";

print "(Should be 6 7 8 9 10)\n";

my @barney = above_average(100, 1..10);

print "\@barney is @barney\n";

print "(Should be just 100)\n";

2. Write a subroutine named greet that welcomes the person you name by telling each new person the names of all the people it has previously greeted:

greet( "Fred" );

greet( "Barney" );

greet( "Wilma" );

greet( "Betty" );

This sequence of statements should print:

Hi Fred! You are the first one here!

Hi Barney! I've seen: Fred

Hi Wilma! I've seen: Fred Barney

Hi Betty! I've seen: Fred Barney Wilma

Answer 1

#!/usr/local/bin/perl

#use diagnostics;
#use warnings;
use Math::Trig;
use utf8;
use strict;
use v5.10;

#exercise 1
#=for comment

sub total {
   my $sum = 0;
   foreach (@_) {
       $sum += $_;
   }
   $sum;
}

my @fred = qw{ 1 3 5 7 9 };
my $fred_total = total(@fred);
print "The total of \@fred is $fred_total.\n";

print "Enter some numbers on separate lines: ";
my $user_total = total(<STDIN>);
print "The total of those numbers is $user_total.\n";
print "\n\n";

#exercise 2
my $sum_of_1_to_1000 = total(1..1000);
print "\$sum_of_1_to_1000 = $sum_of_1_to_1000\n";
print "\n\n";

#=cut

#exercise 3
sub average {
   my $mean = 0;
   foreach (@_) {
       $mean += $_;
   }
   $mean /= @_;
}

sub above_average {
   my $mean = &average(@_);
   my @result;
   foreach (@_) {
       if ($_ > $mean) {
           push @result, $_;
       }
   }
   @result;
}

my @fred = &above_average(1..10);
print "\@fred is @fred\n";
print "(Should be 6 7 8 9 10)\n";

my @barney = above_average(100, 1..10);
print "\@barney is @barney\n";
print "(Should be just 100)\n";
print "\n\n";

#exercise 4
sub greet {
   state $last_name = undef;
   if ($last_name eq undef) {
       print "Hi $_[0]! You are the first one here!\n";
   } else {
       print "Hi $_[0]! $last_name is also here!\n";
   }
   $last_name = $_[0];
}

greet("Fred");
greet("Barney");
print "\n\n";

#exercise 5
sub greet2 {
   state $last_names = undef;
   if ($last_names eq undef) {
       print "Hi $_[0]! You are the first one here!\n";
   } else {
       print "Hi $_[0]! I've seen: $last_names\n";
   }
   if ($last_names ne undef) {
       $last_names .= " ";
   }
   $last_names .= $_[0];
}

greet2( "Fred" );
greet2( "Barney" );
greet2( "Wilma" );
greet2( "Betty" );
print "\n\n";